System and Method for Three-Dimensional Airway Reconstruction, Assessment and Analysis

ABSTRACT

This invention relates to a system and method for three-dimensional airway reconstruction, assessment and analysis. Specifically, the invention relates to a system and method for acquiring one- and two-dimensional data regarding a cavity, such as an esophagus or an airway, and manipulating that data to reconstruct a three-dimensional geometrical object representing that cavity. Suitable data collection methods include, but are not limited to, non-ionizing, non-invasive protocols including acoustic reflectometry, such as that performed by a DOS®- or Windows®-based pharyngometer or rhinometer. The resulting three-dimensional geometric object of the subject cavity can be used to diagnose cavity morphology/obstruction, aid in management and treatment of the obstruction, evaluate efficacy of management and treatment of the obstruction and also provide information for use in outcome analysis and forensic and medico-legal evaluation of diagnosis and treatment of cavity obstruction/stenosis.

BACKGROUND OF THE INVENTION

The invention relates to a system and method for three-dimensionalairway reconstruction, assessment and analysis. Specifically, theinvention relates to a system and method for acquiring one- andtwo-dimensional data regarding a cavity, such as an esophagus or anairway, and manipulating that data to reconstruct a three-dimensionalgeometrical object representing that cavity. Suitable data collectionmethods include, but are not limited to, non-ionizing, non-invasiveprotocols including acoustic reflectometry, such as that performed by aDOS®- or Windows®-based pharyngometer or rhinometer. The resultingthree-dimensional geometric object of the subject cavity can be used fordiagnostics assessments, such as cavity constriction/obstruction, andtherefore aid in the management and treatment of theconstriction/obstruction, evaluate the efficacy of management andtreatment of the constriction/obstruction and also provide informationfor use in outcome analysis, as well as forensic and medico-legalevaluations of diagnosis and treatment of cavityconstriction/obstruction.

1. Field of the Invention

Obstruction/constriction of certain body cavities, such as airwaypassages, can create serious health problems. For example, sleep apneais a debilitating and life-threatening condition that affects peopleworldwide. Sleep apnea occurs when tissues in the upper airway block thebreathing passages. Obstructive sleep apnea is the most common type ofsleep apnea. Normally, the muscles in the upper part of the throat allowair to flow into the lungs. When a person with obstructive sleep apneafalls asleep, these muscles are not able to keep the air passage openall the time. When the airway closes, breathing stops, oxygen levelsfall and sleep is disrupted in order to open the airway. The disruptionof sleep usually lasts only a few seconds. These brief arousals disruptcontinuous sleep and prevent obstructive sleep apnea sufferers fromreaching the deep stages of slumber, such as rapid eye movement (REM)sleep, which the body needs in order to rest and replenish its strength.Once breathing is restored, obstructive sleep apnea sufferers fallasleep only to repeat the cycle throughout the night.

Sleep apnea is suffered by adults and children alike. Sleep apnea cancause the sufferer to be sleepy throughout the day and is associatedwith cardiovascular disorders, including hypertension, coronary arterydisease, heart failure, cardiac arrhythmia, stroke and metabolicabnormalities. Sleep apnea can be treated today by both surgical andnon-surgical approaches. For example, by use of Continuous PositiveAirflow Pressure (“CPAP”), the sufferer wears a mask that supplies asteady stream of air during sleep, where the airflow keeps the nasalpassages open sufficiently to prevent airway collapse and apnea. Weightloss, change of sleep habits, behavior modification and wearing of oralappliances during sleep can also promote normal sleep.

In addition, people suffer from airway obstructions orconstriction/narrowing (stenosis) due to congenital conditions and/oraccidents.

In each case, evaluation of a cavity such as an airway is a valuabletool in analyzing a problem, and then developing a management and/ortreatment plan for the sufferer of the problem. Also, evaluation of acavity such as an airway is useful in providing information on outcomeanalysis for management and/or treatment plans for both care providersand insurance providers. Additionally, evaluation of the cavity hasforensic and medico-legal uses.

2. Description of Related Art

Methods for acquiring data regarding the anatomy of body cavities andorgans are known. For example, techniques such as radiographs (x-rays),including lateral cephalographs; CT scans, including cone-beamtomography, and nuclear MRI are often used to image body organs andcavities for evaluation and diagnostic purposes. These techniques havelimited uses, however. Radiographs, including cephalographs, and CTscans expose the patient to potentially harmful ionizing radiationrequiring appropriate precautions. Also, certain patient groups such aspregnant women might be excluded from such protocols. Also, certaintechniques such as CT scans and nuclear MRI require post-processing ofdata to isolate certain cavities, such as the airway, because alltissues, including skin, muscle, bone, etc., are imaged simultaneously.Other techniques, such as cone-beam tomography, generate huge filesizes, which may exceed the resources available at a typicalcare-provider's office. Additionally, these techniques tend to beexpensive, time-consuming and often require specially trained personnel.

Acoustic reflectometry is a non-invasive, non-ionizing protocol thatproduces a “one-dimensional” curve of the distance into the airwayversus a two-dimensional cross-sectional area map of the upper airway.For example, U.S. Pat. No. 5,316,002, issued to Jackson et al. entitled“Nasopharyngealometric Apparatus and Method,” the disclosure of which isincorporated by reference, discloses an apparatus and method for:determining the profile of the nasopharyngeal cavity by introducingacoustic signals into the nasal cavities of a subject; detecting theacoustic signals and acoustic reflections; generating electrical signalsproportional to the amplitude of the acoustic signals and acousticreflections; determining the length of the nasal septum separating thenasal cavities, and computing the value of the area-distance function ofthe nasopharyngeal cavity from the electrical signals and the length ofthe nasal septum. U.S. Pat. No. 5,823,965, issued to Rasmussen entitled“Device for Reflectometric Examination and Measurement of Cavities,” thedisclosure of which is incorporated by reference, also discloses anapparatus and method for reflectometric examination and measurement ofhuman and animal cavities such as air and food passages. U.S. Pat. Nos.5,746,699 and 5,666,960, both issued to Fredberg et al. and bothentitled “Acoustic Imaging”, the disclosures of which are incorporatedby reference, disclose an apparatus for providing an output signalcharacteristic of the morphology of the respiratory tract. A transducerlaunches acoustical energy toward the opening of the tract, producing anincident wave and a reflected wave to form a transient wave-fieldrepresentative of the morphology of the tract. In each of thesedisclosures, the result is a “two-dimensional” measurement of thecross-sectional area of the measured cavity as a function of a“one-dimensional” distance into the cavity.

Practitioners have used acoustical reflectometry to assess preoperativeand postoperative nasal septal surgery; see LARRY SHEMEN, M.D.,F.R.C.S., F.A.C.S. and RICHARD HAMBURG, M.D., F.A.C.S., “PREOPERATIVEAND POSTOPERATIVE NASAL SEPTAL SURGERY ASSESSMENT WITH ACOUSTICRHINOMETRY,”presented at the Annual Meeting of the American Academy ofOtolaryngology-Head and Neck Surgery, Washington, D.C., Sep. 29-Oct. 2,1996, p. 338. The authors reported that the acoustic rhinometer allowsobjective measurement of nasal cavity volume, which is crucial in thediagnosis of nasal dysfunction. Such objective measurement allows forplanning of appropriate treatment and evaluation of results aftermedical or surgical treatment. The authors also noted that objectivedocumentation of nasal obstruction before and after surgery is beingdemanded by third-party payers, and allows for comparison of alternativeprocedures.

Other practitioners have noted that acoustic reflectometry can detectwithin seconds, and without the use of capnography, characteristic,distinctive and specific area-length profiles for both endrotracheal andesophageal intubation. See DAVID T. RAPHEAL, M.D., PH.D., “ACOUSTICREFLECTOMETRY PROFILES OF ENDOTRACHEAL AND ESOPHAGEAL INTUBATION,”Anesthesiology. 92(5): 1293-1299, May 2000.

Certain practitioners have reported on the size and pressure/arearelationship of the pharynx as important factors in the pathogenesis ofobstructive sleep apnea. See BRIGADIER GENERAL IBRAHIM KAMAL, M.D.,“NORMAL STANDARD CURVE FOR ACOUSTIC PHARYNGOMETRY,” available from theENT Department, Police Authority Hospital, 26 Makram Oubaid Street, NasrCity, Egypt. Dr. Kamal reported that assessment of the upper airway forpossible site(s) of obstruction/constriction is one of the keys tosuccessful management of the condition, and that acoustic pharyngometryhas the potential for localizing such sites. Dr. Kamal further reportedthat the acoustic pharyngometry technique is easy, rapid andcost-effective.

Acoustic reflectometry has also been used in connection with detectionof conditions of the middle ear. For example, U.S. Pat. Nos. 5,868,682and 5,699,809, both issued to Combs et al. and both entitled “Device andProcess for Generating and Measuring the Shape of an AcousticReflectance Curve of an Ear”, the disclosures of which are incorporatedby reference, disclose a device and process for analysis of acousticreflectance of components of an ear. The results can assist in diagnosisof an ear pathology such as abnormal pressure, presence of fluid in themiddle ear or conductive hearing loss.

SUMMARY OF THE INVENTION

The invention relates to a system and method for three-dimensionalairway reconstruction, assessment and analysis. The inventive system andmethod can be performed using data input captured, stored and exportedusing a DOS® or Windows®-based pharyngometer or rhinometer. Athree-dimensional geometric object of the airway can be generated fromthe data input, in contrast to the “one-dimensional” curve of thecross-sectional area of the measured airway as a function of distanceinto the airway that is output from a pharyngometer or rhinometer. Thiscomputer-generated three-dimensional object can be presentedgraphically, and allows care providers to make assessments andcomparisons for diagnostic or treatment purposes. The resultingthree-dimensional geometric object can also be used for objectivedocumentation of nasal obstruction before and after surgery as demandedby third-party payers, or can be used for forensic or medico-legalpurposes.

The inventive system and method is fast, easy to use, does not requirespecialized training for the operator and can run on personal computersand laptops as may be found in a care provider's office. In addition,acoustic reflectometry is a non-ionizing, non-invasive protocol that cansafely be used without the precautions, disadvantages andpost-processing of previously known imaging methods, such asradiographs, including cephalographs, CT scans, including cone-beamtomography and MRI scans.

The resulting geometric object of the airway can be superimposed on atwo-dimensional digital radiograph or digital photograph. Thisfunctionality permits the user to visualize a more anatomically-correctthree-dimensional airway, and may provide the user with furtherinformation on site-specific airway obstruction/constriction e.g.,before and after treatment, with or without an oral appliance etc.

It is therefore an object of the invention to provide a system andmethod to create a reconstructed three-dimensional geometric objectrepresenting a cavity, such as an airway, using one- and two-dimensionalinput data, such as cross-sectional area of an airway measured as afunction of distance from the opening of the airway cavity.

It is another object of the invention to provide a system and method tocreate a reconstructed three-dimensional geometric object representing acavity, such as an airway, using one- and two-dimensional input dataincluding cross-sectional area of an airway measured as a function ofdistance from the opening of the airway cavity using non-ionizing,non-invasive protocols, such as acoustic reflectometry.

It is another object of the invention to provide a system and method tocreate a reconstructed three-dimensional geometric object representing acavity, such as an airway, using one- and two-dimensional input dataincluding cross-sectional area of an airway measured as a function ofdistance from the opening of the airway cavity using acousticreflectometry.

It is yet another object of the invention to provide a system and methodto create a reconstructed three-dimensional geometric objectrepresenting a cavity, such as an airway, using one- and two-dimensionalinput data including cross-sectional area of an airway measured as afunction of distance from the opening of the airway cavity usingacoustic reflectometry techniques including a Pharyngometer™ orrhinometer.

It is yet another object of the invention to superimpose a reconstructedthree-dimensional geometric object representing a cavity, such as anairway, created using one- and two-dimensional input data includingcross-sectional area of an airway as measured as a function of distancefrom the opening of the airway cavity onto a two dimensional digitalradiograph or digital photograph of that cavity.

It is yet another object of the invention to provide a process andsystem for digital manipulation of a reconstructed three-dimensionalgeometric object representing a cavity, such as an airway, created usingone- and two-dimensional input data including cross-sectional area of anairway as measured as a function of distance from the opening of theairway cavity.

It is yet another object of the invention to provide a system and methodfor analyzing cavity characteristics, such as length, area and volume toidentify and quantify airway obstructions/constrictions/narrowing(stenosis), using a reconstructed three-dimensional geometric objectrepresenting a cavity, such as an airway, created using one- andtwo-dimensional input including cross-sectional area of an airwaymeasured as a function of distance from the opening of the airwaycavity.

It is yet another object of the invention to provide a system and methodfor assessing/evaluating treatment methods/protocols to manage and/oralleviate cavity dysfunction, such as airway obstructions, using areconstructed three-dimensional geometric object representing a cavity,such as an airway, created using one- and two-dimensional input dataincluding cross-sectional area of an airway measured as a function ofdistance from the opening of the airway cavity.

It is yet another object of the invention to provide a system and methodfor assessing/evaluating the efficacy of treatments of and/or managementof cavity obstructions, such as airway obstructions, using areconstructed three-dimensional geometric object representing a cavity,such as an airway, created using one- and two-dimensional input dataincluding cross-sectional area of an airway measured as a function ofdistance from the opening of the airway cavity.

The system and method of the invention include a programmable processorfor receiving one- and two-dimensional data representing cross-sectionalarea and distance of a cavity, such as an airway, measured from theopening of the cavity; calculating a plurality of circles, whichrepresent the cross-sectional area of the cavity at known distances fromthe starting point (the opening of the cavity) and from each other(adjacent circular cross-sectional areas) from the input data; forming atriangular mesh from the plurality of circles that represent thecross-sectional area of the cavity; and creating output data including athree-dimensional geometric object comprising the triangular meshrepresentative of the cavity enclosed by a rendered surface, along withother data representing length, area and volume parameters of thecavity. The three-dimensional geometric object can be manipulated toevaluate and compare the management and/or treatment of any conditionsof the cavity, such as obstruction of an airway. Further, differentthree-dimensional geometric objects can be compared to evaluate pre- andpost-treatment efficacy due to management and/or treatment of thecavity, such as an obstruction of an airway. Additionally, thethree-dimensional geometric object can be superimposed on a digitalradiograph or digital photograph of the cavity to permit the user tovisualize a more anatomically-correct three-dimensional airway, andprovide the user with further information on site-specific airwayobstruction/constriction.

Further, different three-dimensional geometric objects can bemanipulated to compute an averaged or mean cavity, such as an averageairway. Furthermore, these averaged or mean objects can be compared fordiagnostic or treatment planning purposes.

Yet further, groups of different three-dimensional geometric objects canbe represented and plotted in statistical space, so that a new,three-dimensional geometric object can be compared to evaluate thechances of that new object being in the same group or a different groupwith respect to the three-dimensional geometric objects plotted.

These and other features of various embodiments will become readilyapparent to those skilled in the art upon review of the detaileddescription that follows.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a graph depicting a one-dimensional curve obtainable from anacoustic reflectometry device, such as a Pharyngometer™ or rhinometer,and showing the cross-sectional area of a measured airway as a functionof distance from the opening of the airway.

FIG. 2 is a table showing typical output data of an acousticreflectometry device, such as a Pharyngometer™ or rhinometer.

FIG. 3 is a schematic diagram of the system of the invention.

FIG. 4 is a graphic depicting a three-dimensional geometric object of acavity, such as an airway, created using output data such as that shownin FIG. 2.

FIG. 5 is a flowchart depicting the steps performed in one embodiment ofthe method of the invention.

FIG. 6 is a depiction of a reconstructed three-dimensional geometricobject of an airway superimposed on a digital radiograph of thecorresponding patient, according to one embodiment of the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

For the purposes of promoting an understanding of the embodimentsdescribed herein, reference will be made to preferred embodiments andspecific language will be used to describe the same. The terminologyused herein is for the purpose of describing particular embodimentsonly, and is not intended to limit the scope of the present invention.As used throughout this disclosure, the singular forms “a,” “an,” and“the” include plural reference unless the context clearly dictatesotherwise. Thus, for example, a reference to “a composition” includes aplurality of such compositions, as well as a single composition, and areference to “a geometric object” is a reference to one or moregeometric objects and equivalents thereof known to those skilled in theart, and so forth.

Acoustic reflectometry provides one- and two-dimensional information ona cavity. For example, the Eccovision Acoustic Pharyngometer® and/orEccovision Acoustic Rhinometer® manufactured by Hood Laboratories,located in Pembroke, Mass. and distributed by Sleep Group Solutions LLCof Miami, Fla., are non-invasive, non-ionizing protocols that candetermine the dimensions of the oral airway past the epiglottis or thenasal cavity. Details on the operation of the Eccovision AcousticPharyngometer® and/or Eccovision Acoustic Rhinometer® are available fromHood Laboratories, and are hereby incorporated by reference. The outputof the Eccovision Acoustic Pharyngometer® and/or Eccovision AcousticRhinometer® is a one-dimensional graph/curve providing information onthe cross-sectional area of the oral airway past the epiglottis or nasalcavity as a function of the distance into the oral airway past theepiglottis or nasal cavity. FIG. 1 depicts a typical output for aEccovision Acoustic Pharyngometer™ and an Eccovision AcousticRhinometer™.

The system and method of the invention processes the data acquired fromthe Eccovision Acoustic Pharyngometer® and/or Eccovision AcousticRhinometer® to create a three-dimensional geometric object depicting theoral airway past the epiglottis or the nasal cavity. The output of theEccovision Acoustic Pharyngometer® and/or Eccovision AcousticRhinometer® are files containing a sequence of distances (d0, d1, . . ., dn−1) and the corresponding cross-sectional areas (A0, A1, . . . An−1)of the oral or nasal airway past the epiglottis or nasal cavity,respectively. A table depicting the typical file content from theEccovision Acoustic Pharyngometer® and/or Eccovision AcousticRhinometer® is included in FIG. 2. A graph of these data provides acurve similar to that shown in FIG. 1.

The system 300 of the invention is depicted in FIG. 3, and includes aprocessor 310 programmed to process data acquired from an EccovisionAcoustic Pharyngometer® and/or Eccovision Acoustic Rhinometer® from acavity to be measured. Typically, data measured by the EccovisionAcoustic Pharyngometer® and/or Eccovision Acoustic Rhinometer® arecaptured, stored and saved in proprietary format, and then exported tothe system of the invention 300 over link 320. The acquired data arethen stored as simple ASCII or text files 330 _(i) in a storage unit340. The stored files 330 _(i) are processed by the processor 310according to programmed algorithms that encode a method forthree-dimensional airway reconstruction, assessment and analysis.Alternatively, the acquired data can be processed directly by theprocessor 310 to provide a reconstructed three-dimensional airway orcavity. The system 300 can be installed on a personal computer orlaptop.

The processor 310 checks the acquired data for format, including errorsduring data capture and consistency and modifies the data if necessaryprior to storage in files 330 _(i) in the data storage area 340.Alternatively, the acquired data can be checked for format prior toprocessing, if the acquired data are to be processed prior to storage infiles 330 _(i) in data storage area 340. For example, measurementsassociated with the acoustic reflectometer tube are discarded, as wellas null pairs and repeated distances. Details on the operation of thePharyngometer and Rhinometer are available and on how the data areinitially processed are available from Hood Laboratories, and are herebyincorporated by reference. The data storage area 340 that is used tostore the data that is acquired from the Eccovision AcousticPharyngometer® and/or Eccovision Acoustic Rhinometer® can include anystorage now known or later developed, and can include a 3.5″ floppydisk, ZIP disk, CD, USB-drive or mini hard-drive.

The processor 310 upon command retrieves a stored file 330 _(i), andthen processes the acquired data stored in file 330 _(i) according tothe method of the invention to create output data 350 _(i) that can begraphed to form a three-dimensional geometric object representative ofthe cavity, along with other data representative of length, area andvolume parameters of the cavity. FIG. 4 depicts typical graphicaloutputs of three-dimensional geometrical objects of a cavity createdusing one- and two-dimensional data acquired from an acousticreflectometer, such as the Eccovision Acoustic Pharyngometer® and/orEccovision Acoustic Rhinometer®. Alternatively, output data 350 _(i) canbe obtained by directly processing and graphing acquired data from theacoustic reflectometer, without first storing the acquired data in afile 330 _(i) in data storage area 340. The output data 350 _(i) can bestored in the data storage area 340 or exported if required or desired.

The processor 310 is further programmed to retrieve and compare outputdata 350 _(i) to other data, including standardized data or datarelating to the same cavity but taken at different points in time, suchas pre-treatment and post-treatment. Such comparison may be useful fordiagnostic and treatment planning purposes, measuring efficacy ofmanagement and/or treatment of conditions of the cavity, such asobstructions/narrowing of the airway, for example to compareeffectiveness of pre- and post-management and treatment of the cavity.The processor 310 can be further programmed to manipulate the storedoutput data 350 _(i) to evaluate management and/or treatment of anyconditions of the cavity, such as obstruction/narrowing of an airway.Additionally, the processor 310 can be programmed to superimpose thestored output data 350 _(i) on a digital radiograph or digitalphotograph of the cavity to permit a user to visualize a moreanatomically-correct 3-D airway, and provide the user with furtherinformation on site-specific airway obstruction/constriction, as seen inFIG. 6. A display unit 360 can be placed in communication with theprocessor 310 or with any system to which output data 350 _(i) may beexported that can graphically display the output data 350 _(i) as wellas the manipulations of the output data 350 _(i), using standardpersonal computer monitors and similar visual display units.Additionally, the output data 350 _(i) can be exported or printed onvarious media using standard personal computer printers and peripherals.Alternatively, output data 350 _(i) can be compared to other images, bedisplayed on display unit 360, or manipulated without first storing theoutput data 350 _(i) in data storage area 340.

As known to those skilled in the art, the Eccovision AcousticPharyngometer® and/or Eccovision Acoustic Rhinometer® are operable usingstandard DOS® and Windows® operating systems installed on personalcomputers. The processors of those computer systems can easily performthe processing steps to manipulate the acquired data to provide thegeometric objects depicting the cavity according to the invention, andthe output data files 350 _(i) are of a size that computer systems foundin typical care-provider offices can easily store a plurality of suchfiles.

A flow scheme of the method of the invention is depicted in FIG. 5. At500, data are measured using an acoustic reflectometer, such as anEccovision Acoustic Pharyngometer® and/or Eccovision AcousticRhinometer®, from a cavity. The Eccovision Acoustic Pharyngometer®and/or Eccovision Acoustic Rhinometer® can be operated at standardoperating conditions, as described in literature available from HoodLaboratories and as known to those skilled in the art. The measured dataare acquired by the processor 310 of the system of the invention at 510.At 520, the acquired data are checked by the processor 310 for format,including errors during data capture and consistency, and stored infiles 330 _(i) in the storage unit 340 if the files are acceptableaccording to predetermined protocols and standards. The stored files 330_(i) are retrieved by the processor 310 at 530, and the data stored inthe stored files 330 _(i) are processed at 540 according to the methodof the invention to create output data 350 _(i) that can be graphed toform a three-dimensional geometric object representative of the cavity,along with other data representative of length, area and volumeparameters of the cavity. FIG. 4 depicts typical graphical outputs ofthree-dimensional geometrical objects of a cavity created using one- andtwo-dimensional data acquired from an acoustic reflectometer, such asEccovision Acoustic Pharyngometer® and/or Eccovision AcousticRhinometer®. In another embodiment, acquired data is processed byprocessor 310 at 540 directly prior to storage in files 330 _(i). Theoutput data 350 _(i) can be stored at 540 in the data storage area 340or exported if required or desired.

At 550, the processor 310 may retrieve and compare output data 350 _(i)from a plurality of stored files 330 _(i) for diagnostic and treatmentplanning purposes, measuring efficacy of management and/or treatment ofconditions of the cavity, such as obstructions/narrowing of the airway,for example to compare effectiveness of pre- and post-management andtreatment of the cavity. At 560, the processor 310 can furthermanipulate the stored output data 350 _(i) to evaluate management and/ortreatment of any conditions of the cavity, such as obstruction/narrowingof an airway. At 570, the processor 330 can superimpose the storedoutput data 350 _(i) on a digital radiograph or digital photograph ofthe cavity to permit a user to visualize a more anatomically-correctthree-dimensional airway, and provide the user with further informationon site-specific airway obstruction/constriction. At 580, the outputdata 350 _(i) can be graphically displayed on display unit 360 as wellas the manipulations of the output data 350 _(i). At 590, the outputdata 350 j can be exported or printed on various media using standardpersonal computer printers and peripherals. Any of steps 550 through 590can be performed individually or in combination with any other step, ormay be performed in any order desired by the user of the system andmethod of the invention. In one embodiment, output data 350 _(i) are notstored in data storage area 340 as shown in 550 and then retrieved priorto comparison, manipulation and/or superimposition, but rather outputdata 350 _(i) can be used for comparison, manipulation and/orsuperimposition purposes and applications substantially directly afterprocessing of the acquired data by processor 310.

The method of the invention uses programmed algorithms that encode amethod for three-dimensional airway reconstruction, assessment andanalysis. The method begins using data acquired from an acousticreflectometer, which data comprise n data points, including distance andcorresponding cross-sectional area as shown in FIG. 2. A plurality ofcircles, each having a plurality of nodes, are generated from theacquired data as follows.

Each circle represents the corresponding cross-sectional area at a knowndistance as recorded and captured using an acoustic reflectometer, suchas an Eccovision Acoustic Pharyngometer® and/or Eccovision AcousticRhinometer®. The number of nodes and the number of circles arecalculated when n two-dimensional points are acquired and a netthree-dimensional surface is obtained having nl times nr nodes, where nlcan be equal or not to n.

Each node represents homologous points on each circle. In oneembodiment, the number of nodes per circle nr equals 40, but this can bechanged according to the requirements of the user in order to increaseor decrease resolution of the three-dimensional object that isgenerated. For example, a featureless (smooth) three-dimensional objectindicates that default settings should be increased, while excessiveresolution can result in a correspondingly large file size and defaultvalues may be decreased, if desired or if necessary. Those of ordinaryskill in the art will be able to select other values of nr to providedesired results to provide a desired three-dimensional object and filesize.

The number of circles, or nl, is then calculated by the formula:

nl=nr(dmax/2πrave)

where dmax and rave are calculated from the acquired data and comprisethe maximum distance d from the origin of the cross-sectional area of ameasured cavity area having radius r[i], and rave comprises the averageradius of the cross-sectional areas of the measured cavity area. Whenprocessing the acquired data, new radii can be interpolated according tothe requirements of the user. Typically, nr will equal or exceed atleast 3 and nl will equal or exceed at least 2, but there is no limit onthe upper value limit of nr and nl. However, the value for nl is relatedto the data input from the acoustic reflectometer.

nl times nr nodes are then generated using the following formulae:

x[i][k]=D[i];

y[i][k]=R[i]*cos(cita(k)); and

z[i][k]=R[i]*sin(cita(k)),

where D[i] is the distance of the cross-sectional area from the origin,cita(k) moves step by step from 0 to 180 degrees (nr steps), and i goesfrom 0 to (nl−1). The nodes obtained are then morphed, or bent, startingfrom three parameters: dPC1, dPC2 and dAngle. This process provides amore anatomically correct airway, since the default data input from theacoustic reflectometer provides a “straight tube.” These parameters areselected according to the patient's anatomical features. For example,the data input from the acoustic reflectometer starts at the teeth ornostril. The user of the system and method of the invention can decidewhere to bend the “straight tube” by examining the correspondingpatient's lateral cephalograph or by other measurements or techniques,knowing that certain features of the “straight tube” (for example, itsnarrowest part) are to be superimposed on the epiglottis of thecorresponding patient's lateral cephalograph. During superimposition,the user has enough elements to morph the airway according to thecorresponding patient's radiograph. dPC1 represents the site wherebending will begin, dPC2 represents the site where bending will end anddAngle represents the angle at which the “straight tube” will be bentbetween these two sites.

The number of rotations performed in the morphing step are calculated asfollows:

nl(dPC2−dPC1)/100=# rotations,

where the first [nl*(dPC1/100)] circles are not transformed. Forexample, where nl=100, dPC1=30%, dPC2=70% and dAngle=45°, 40 rotationswould be executed, and the first 30 circles are not transformed. Theresulting rotation is then distributed evenly per circle over the siteto be bent such that bending is implemented by rotation of the circleslocated between dPC1 and dPC2. In this example, the following rotationsare carried out:

Circles simultaneously Rotation Number Rotation angle rotated 1 45°/40 =1.125° 31, 32, 33, 34, 35 . . . 99 2 45°/40 = 1.125° 32, 33, 34, 35 . .. 99 3 45°/40 = 1.125° 33, 34, 35 . . . 99 . . . . . . . . . 40  45°/40= 1.125° 70 . . . 99

In performing the rotations, in the first rotation the first circle aswell as all of the following circles are rotated simultaneously. In thesecond rotation, the second circle as well as all of the followingcircles are rotated simultaneously, but the first circle (or, in thecase of the third and later rotations, all circles before them) remainunchanged.

The plurality of nodes following the morphing step describes thethree-dimensional form, or geometric object, of the cavity. Thegenerated circles comprising the generated nodes are connected to form atriangular mesh, as shown in FIG. 4. The triangles are generated bystandard triangulation routines known to those of ordinary skill in theart.

Once the triangles are generated from the acquired data and connected tocreate the final form as seen in FIG. 4, the final form can be bent ormorphed, using a spline interpolation. The final form can be bent ormorphed in the three planes of space to any angle between 0-360°. Thisprocess involves comparing homologous triangular finite elements ascalculated from the acquired data using finite element analysis. FIG. 4depicts a reconstructed three-dimensional object representing a portionof an airway, having eighty (80) nodes.

Finite element analysis consists of a computer model of a material ordesign that is stressed and analyzed for specific results. Finiteelement analysis can be used to modify an existing structure to analyzethe structure under a new condition, and can be used to determine designmodifications to meet the new condition. Finite element analysis uses acomplex system of points called nodes which make a grid called a mesh,which mesh is programmed to contain the material and structuralproperties which define how the structure will react to certain loadingconditions. Nodes are assigned at a certain density throughout thematerial depending on the anticipated stress levels of a particulararea. Regions which will receive large amounts of stress usually have ahigher node density than those which experience little or no stress.

In this case, the nodes are homologous landmarks evenly distributedthroughout the form. The mesh acts like a spider web in that from eachnode, there extends a mesh element to each of the adjacent nodes. Fromthese data, area factor, deformation factor and principal axes arecalculated which are useful for detecting changes in size (e.g. length,area or volume), changes in shape (e.g. a sphere (soccer ball) changinginto an ellipsoid (football) of the same volume), and the directionalityin which those changes occurred (e.g. in the vertical, horizontal ortransverse axes). The parameters to be taken into account duringtransformation of the final form include circumference diameter D;circumference area Ac; ellipse major axis S1; ellipse minor axis S2;ellipse area Ae; unit vector along S1 axis e1; and unit vector along S2axis e2. From these values, the following factors can be calculated thatare used to describe mathematically how the triangle was transformed:

Area factor fA=Ae/Ac

Deformation factor fD=S1/S2

Principal axis direction e1

Those of ordinary skill in the art of finite element analysis cancalculate these parameters without undue experimentation.

The ability to transform the final form aids in evaluating managementand/or treatment methods of conditions of the cavity. For example,management and/or treatment of sleep apnea may be aided by transformingthe final form to determine the parameters of certain treatments, suchas oral appliances or the settings for CPAP.

The final form as represented by the output data 350 _(i) which iscreated by connecting the triangular mesh can be stored in the datastorage unit 340. The output data 350 _(i) includes data regardinglengths, areas and volumes of the cavity. The final form can also bedisplayed on a display unit 360, using surface rendering. While on thedisplay unit 360, the final form output data 350 _(i) can besuperimposed on other three-dimensional data or on two-dimensionaldigital radiographs or digital photographs of the cavity. FIG. 6 depictsthe superimposition of a final form of a reconstructed three-dimensionalobject representing an airway onto a digital radiograph of thecorresponding patient's airway. This functionality permits the user tovisualize a more anatomically-correct three-dimensional airway, and mayprovide the user with further information on site-specific airwayobstruction/constriction e.g., before and after treatment, with orwithout an oral appliance, etc.

Stored forms can be compared to other stored forms, as well. Forexample, using finite-element analysis, a stored form of a normalsubject can be compared with the stored form of a patient with sleepapnea, having the same number of nodes. Using a pseudocolor-coded scale,the user can evaluate the degree of severity of the condition, usingfinite-element analysis to localize and quantify the changes. As well,an average form can be computed for a population. For example, theaverage airway of adult males can be compared with the average airway ofadult females. Similarly, the average airway of boys can be comparedwith the average airway of girls, etc.

The output data 350 _(i) is useful for many purposes, including but notlimited to analysis of airway obstructions/constrictions and analysis ofmanagement/treatment options; determination of efficacy of treatment ofairway obstructions by comparison of pre- and port-treatment outputdata; objective measurement of efficacy of treatment for use by thirdparties, such as insurance carriers; and forensic and medicolegalapplications.

It is possible to extend the inventive system and method tothree-dimensional elements as well. Triangles are replaced by pyramids(tetrahedrons) with four landmarks as vertices. The circumference insidethe triangle becomes a sphere inside the pyramid, which is transformedinto an ellipsoid. Area factor is replaced by Volume factor, and twodeformation factors and three parameters are required to defineellipsoid orientation. In this context, only Volume factor is consideredfor pyramids.

Frequently, three-dimensional forms are described by the envelopingsurface, which is mathematically simulated by a mesh composed of a largenumber of triangular elements that are transformed simultaneously withthe transformation. Area and deformation factors can also be obtainedfor these triangular elements.

Although the system and method was described in terms of data measuredby an acoustic reflectometer of an airway cavity, the system and methodis also suitable for other types of data and other cavity measurementswhere three-dimensional reconstruction and analysis would be desirablesuch as tracheal stenosis, either analog or digital. Other suitablemodifications and adaptations of the variety of conditions andparameters normally encountered in therapy are within the spirit andscope of the invention.

1-9. (canceled)
 10. A computer-implemented method of reconstructing,assessing and analyzing a three-dimensional representation of a cavitycomprising: receiving data measured by an acoustic reflectometerrepresentative of the cross-sectional area of a cavity of an objectmeasured at a plurality of distances from an origin point of the cavity;storing a plurality of data files, the data files comprising thereceived data; converting the received data into a three-dimensionalgraphical representation of the cavity by calculating a plurality ofnodes based on the received cross-sectional area and distance data,forming a plurality of circles based on the calculated nodes, rotatingthe plurality of circles in accordance with the features of the cavityand the object and connecting the nodes following rotation of theplurality of circles to form a triangular mesh; and storing theconverted data in the storage unit.
 11. The method of claim 10, furthercomprising displaying the three-dimensional representation of the cavitya display unit.
 12. The method of claim 10, wherein the object comprisesa mammal.
 13. The method of claim 12 wherein the object comprises ahuman being.
 14. The method of claim 10, wherein the cavity comprises anairway.
 15. The method of claim 10, wherein the acoustic reflectometercomprises one of a pharyngometer or a rhinometer.
 16. The method ofclaim 10, further comprising manipulating the three-dimensionalrepresentation of the cavity to analyze the effect of a new condition ofthe cavity.
 17. The method of claim 16, further comprising measuringchanges in size, changes in shape and the directionality of changes tothe cavity under a new condition.
 18. The method of claim 10, furthercomprising superimposing the three-dimensional representation of thecavity on a digital radiograph or digital photograph of the cavity. 19.A computer-implemented method of evaluating efficacy of treatment of acondition of an airway comprising: receiving data measured by anacoustic reflectometer representative of the cross-sectional area of acavity of an object measured at a plurality of distances from an originpoint of the cavity; storing a plurality of data files, the data filescomprising the received data; converting the received data into athree-dimensional graphical representation of the cavity by calculatinga plurality of nodes based on the received cross-sectional area anddistance data, forming a plurality of circles based on the calculatednodes, rotating the plurality of circles in accordance with the featuresof the cavity and the object and connecting the nodes following rotationof the plurality of circles form a triangular mesh; storing theconverted data in the storage unit; manipulating the three-dimensionalrepresentation of the cavity to analyze the effect of a new condition ofthe cavity; and designing a treatment of the cavity based on the resultsof the manipulation.
 20. The method of claim 19, wherein the cavitycomprises an airway.
 21. The method of claim 20, wherein the acousticreflectometer comprises one of a pharynogometer or a rhinometer.